On the structure of cytolipin R, a ceramide tetrahexoside hapten from rat lymphosarcoma

Cytolipin R, a ceramide tetrahexoside isolated from rat lymphosarcoma, was studied by sequential hydrolysis with specific glycosidases which revealed the anomeric configurations of the glycosidic bonds. Sugar linkages were established by combined gas-liquid chromatography and mass spectrometry of the partially methylated alditol acetates prepared after permethylation and hydrolysis of the intact lipid. Results indicated the structure of cytolipin R to be N-acetylgalactosaminyl(beta1-->3)galactosyl(alpha1-->3) galactosyl(beta1-->4)glucosyl ceramide. Cytolipin K (globoside I) differs in having a -galactosyl(alpha1-->4)galactosyl- internal linkage, and this difference must account for the immunological differences between cytolipin K and cytolipin R.